This work, entitled VERUM FACTUM VS PRIMUM VERUM. HISTORIA Y POESIA EN GIAMBATTISTA VICO, makes an approach to the philosophical thought of Giambattista Vico and his critique of Cartesian rationalism. In this direction, the Neapolitan defends the role of sensitivity and fantasy in the human cognitive processes. The first chapter opens with a discussion of the Cartesian cogito theory considered the first truth. It is shown how the Neapolitan assumes, initially in a positive way, the approaches of the modern thinker. Later on, however, his criticism goes to the heart of the cogito. The second chapter shows how the work of the Neapolitan is related to the search of a science of man not obtained by the clear and distinct method of Physical-Mathematical Sciences. Such a science is identified with History divided into three ages (age of gods, heroes, men). Vico holds that man can acquire knowledge of the human world because he himself has done it. Consequently, History responds perfectly to the principle Verum factum est. In the third chapter, in order to demonstrate the relationship between History and Poetry, Vico s theory of the fantastic universals and his understanding of the courses and re-courses is explained. Thence we can understand the appropriation Vico makes of the two great poets: Homer, placed in the heroic age, expresses the course of nations, and Dante, at the end of the age of men, expresses the re-course.